/*
 * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package com.sun.naming.internal;

import java.io.InputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URLClassLoader;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.util.Properties;

import javax.naming.*;

/**
 * VersionHelper was used by JNDI to accommodate differences between
 * JDK 1.1.x and the Java 2 platform. As this is no longer necessary
 * since JNDI's inclusion in the platform, this class currently
 * serves as a set of utilities for performing system-level things,
 * such as class-loading and reading system properties.
 *
 * @author Rosanna Lee
 * @author Scott Seligman
 */

final class VersionHelper12 extends VersionHelper {

    // Disallow external from creating one of these.
    VersionHelper12() {
    }

    public Class<?> loadClass(String className) throws ClassNotFoundException {
        return loadClass(className, getContextClassLoader());
    }

    /**
     * Package private.
     *
     * This internal method is used with Thread Context Class Loader (TCCL),
     * please don't expose this method as public.
     */
    Class<?> loadClass(String className, ClassLoader cl) throws ClassNotFoundException {
        Class<?> cls = Class.forName(className, true, cl);
        return cls;
    }

    /**
     * @param className A non-null fully qualified class name.
     * @param codebase A non-null, space-separated list of URL strings.
     */
    public Class<?> loadClass(String className, String codebase) throws ClassNotFoundException, MalformedURLException {

        ClassLoader parent = getContextClassLoader();
        ClassLoader cl = URLClassLoader.newInstance(getUrlArray(codebase), parent);

        return loadClass(className, cl);
    }

    String getJndiProperty(final int i) {
        return AccessController.doPrivileged(new PrivilegedAction<String>() {
            public String run() {
                try {
                    return System.getProperty(PROPS[i]);
                } catch (SecurityException e) {
                    return null;
                }
            }
        });
    }

    String[] getJndiProperties() {
        Properties sysProps = AccessController.doPrivileged(new PrivilegedAction<Properties>() {
            public Properties run() {
                try {
                    return System.getProperties();
                } catch (SecurityException e) {
                    return null;
                }
            }
        });
        if (sysProps == null) {
            return null;
        }
        String[] jProps = new String[PROPS.length];
        for (int i = 0; i < PROPS.length; i++) {
            jProps[i] = sysProps.getProperty(PROPS[i]);
        }
        return jProps;
    }

    InputStream getResourceAsStream(final Class<?> c, final String name) {
        return AccessController.doPrivileged(new PrivilegedAction<InputStream>() {
            public InputStream run() {
                return c.getResourceAsStream(name);
            }
        });
    }

    InputStream getJavaHomeLibStream(final String filename) {
        return AccessController.doPrivileged(new PrivilegedAction<InputStream>() {
            public InputStream run() {
                try {
                    String javahome = System.getProperty("java.home");
                    if (javahome == null) {
                        return null;
                    }
                    String pathname = javahome + java.io.File.separator + "lib" + java.io.File.separator + filename;
                    return new java.io.FileInputStream(pathname);
                } catch (Exception e) {
                    return null;
                }
            }
        });
    }

    NamingEnumeration<InputStream> getResources(final ClassLoader cl, final String name) throws IOException {
        Enumeration<URL> urls;
        try {
            urls = AccessController.doPrivileged(new PrivilegedExceptionAction<Enumeration<URL>>() {
                public Enumeration<URL> run() throws IOException {
                    return (cl == null) ? ClassLoader.getSystemResources(name) : cl.getResources(name);
                }
            });
        } catch (PrivilegedActionException e) {
            throw (IOException) e.getException();
        }
        return new InputStreamEnumeration(urls);
    }

    /**
     * Package private.
     *
     * This internal method returns Thread Context Class Loader (TCCL),
     * if null, returns the system Class Loader.
     *
     * Please don't expose this method as public.
     */
    ClassLoader getContextClassLoader() {

        return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
            public ClassLoader run() {
                ClassLoader loader = Thread.currentThread().getContextClassLoader();
                if (loader == null) {
                    // Don't use bootstrap class loader directly!
                    loader = ClassLoader.getSystemClassLoader();
                }

                return loader;
            }
        });
    }

    /**
     * Given an enumeration of URLs, an instance of this class represents
     * an enumeration of their InputStreams.  Each operation on the URL
     * enumeration is performed within a doPrivileged block.
     * This is used to enumerate the resources under a foreign codebase.
     * This class is not MT-safe.
     */
    class InputStreamEnumeration implements NamingEnumeration<InputStream> {

        private final Enumeration<URL> urls;

        private InputStream nextElement = null;

        InputStreamEnumeration(Enumeration<URL> urls) {
            this.urls = urls;
        }

        /*
         * Returns the next InputStream, or null if there are no more.
         * An InputStream that cannot be opened is skipped.
         */
        private InputStream getNextElement() {
            return AccessController.doPrivileged(new PrivilegedAction<InputStream>() {
                public InputStream run() {
                    while (urls.hasMoreElements()) {
                        try {
                            return urls.nextElement().openStream();
                        } catch (IOException e) {
                            // skip this URL
                        }
                    }
                    return null;
                }
            });
        }

        public boolean hasMore() {
            if (nextElement != null) {
                return true;
            }
            nextElement = getNextElement();
            return (nextElement != null);
        }

        public boolean hasMoreElements() {
            return hasMore();
        }

        public InputStream next() {
            if (hasMore()) {
                InputStream res = nextElement;
                nextElement = null;
                return res;
            } else {
                throw new NoSuchElementException();
            }
        }

        public InputStream nextElement() {
            return next();
        }

        public void close() {
        }
    }
}
